'\" t
.\" Copyright 2000 Nicolás Lichtmaier <nick@debian.org>
.\" Created 2000-07-22 00:52-0300
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" Modified 2002-07-23 19:21:35 CEST 2002 Walter Harms
.\" <walter.harms@informatik.uni-oldenburg.de>
.\"
.\" Modified 2003-04-04, aeb
.\"
.TH encrypt 3 2023-02-05 "Linux man-pages 6.03"
.SH NAME
encrypt, setkey, encrypt_r, setkey_r \- encrypt 64-bit messages
.SH LIBRARY
Encryption and decryption library
.RI ( libcrypto ", " \-lcrypto )
.SH SYNOPSIS
.nf
.BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
.B #include <unistd.h>
.PP
.BI "[[deprecated]] void encrypt(char " block "[64], int " edflag );
.PP
.BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
.B #include <stdlib.h>
.PP
.BI "[[deprecated]] void setkey(const char *" key );
.PP
.BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
.B #include <crypt.h>
.PP
.BI "[[deprecated]] void setkey_r(const char *" key ", struct crypt_data *" data );
.BI "[[deprecated]] void encrypt_r(char *" block ", int " edflag ,
.BI "                              struct crypt_data *" data );
.fi
.SH DESCRIPTION
These functions encrypt and decrypt 64-bit messages.
The
.BR setkey ()
function sets the key used by
.BR encrypt ().
The
.I key
argument used here is an array of 64 bytes, each of which has
numerical value 1 or 0.
The bytes key[n] where n=8*i-1 are ignored,
so that the effective key length is 56 bits.
.PP
The
.BR encrypt ()
function modifies the passed buffer, encoding if
.I edflag
is 0, and decoding if 1 is being passed.
Like the
.I key
argument, also
.I block
is a bit vector representation of the actual value that is encoded.
The result is returned in that same vector.
.PP
These two functions are not reentrant, that is, the key data is
kept in static storage.
The functions
.BR setkey_r ()
and
.BR encrypt_r ()
are the reentrant versions.
They use the following
structure to hold the key data:
.PP
.in +4n
.EX
struct crypt_data {
    char keysched[16 * 8];
    char sb0[32768];
    char sb1[32768];
    char sb2[32768];
    char sb3[32768];
    char crypt_3_buf[14];
    char current_salt[2];
    long current_saltbits;
    int  direction;
    int  initialized;
};
.EE
.in
.PP
Before calling
.BR setkey_r ()
set
.I data\->initialized
to zero.
.SH RETURN VALUE
These functions do not return any value.
.SH ERRORS
Set
.I errno
to zero before calling the above functions.
On success,
.I errno
is unchanged.
.TP
.B ENOSYS
The function is not provided.
(For example because of former USA export restrictions.)
.SH VERSIONS
Because they employ the DES block cipher,
which is no longer considered secure,
.BR encrypt (),
.BR encrypt_r (),
.BR setkey (),
and
.BR setkey_r ()
were removed in glibc 2.28.
Applications should switch to a modern cryptography library, such as
.BR libgcrypt .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR encrypt (),
.BR setkey ()
T}	Thread safety	MT-Unsafe race:crypt
T{
.BR encrypt_r (),
.BR setkey_r ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH STANDARDS
.BR encrypt (),
.BR setkey ():
POSIX.1-2001, POSIX.1-2008, SUS, SVr4.
.PP
The functions
.BR encrypt_r ()
and
.BR setkey_r ()
are GNU extensions.
.SH NOTES
.SS Availability in glibc
See
.BR crypt (3).
.SS Features in glibc
In glibc 2.2, these functions use the DES algorithm.
.SH EXAMPLES
.\" [[deprecated]] SRC BEGIN (encrypt.c)
.EX
#define _XOPEN_SOURCE
#include <crypt.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main(void)
{
    char key[64];
    char orig[9] = "eggplant";
    char buf[64];
    char txt[9];

    for (size_t i = 0; i < 64; i++) {
        key[i] = rand() & 1;
    }

    for (size_t i = 0; i < 8; i++) {
        for (size_t j = 0; j < 8; j++) {
            buf[i * 8 + j] = orig[i] >> j & 1;
        }
        setkey(key);
    }
    printf("Before encrypting: %s\en", orig);

    encrypt(buf, 0);
    for (size_t i = 0; i < 8; i++) {
        for (size_t j = 0, txt[i] = \[aq]\e0\[aq]; j < 8; j++) {
            txt[i] |= buf[i * 8 + j] << j;
        }
        txt[8] = \[aq]\e0\[aq];
    }
    printf("After encrypting:  %s\en", txt);

    encrypt(buf, 1);
    for (size_t i = 0; i < 8; i++) {
        for (size_t j = 0, txt[i] = \[aq]\e0\[aq]; j < 8; j++) {
            txt[i] |= buf[i * 8 + j] << j;
        }
        txt[8] = \[aq]\e0\[aq];
    }
    printf("After decrypting:  %s\en", txt);
    exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR cbc_crypt (3),
.BR crypt (3),
.BR ecb_crypt (3)
.\" .BR fcrypt (3)
